particle size and distribution affect the processability and rheological characteristics of solids-loaded plastic matrix materials; also, for solid rocket motor propellant materials, the burn rate is significantly affected. The kinds of solid particles (e.g., cyclotetramethylenetetranitroamine {HMX}, ammoniumperchlorate {AP}, and metallic aluminum powder) distributed within the polymer matrix of a multi-component solid rocket motor propellant material can usually be made distinguishable from one another by various techniques. For example, aluminum particles are not crystalline and are often spheroid; HMX solids are more readily decomposable by electron beam irradiation at 8 to 30 kilovolts than AP solids. Also refractive index masking oils can mask particles with the same refracting index from view when evaluation is being carried out under an optical microscope.
It is impractical to optically count particles smaller than about two microns across; furthermore optical methods for sizing and counting particles are labor intensive, and refractive index matching oils are often carcinogenic. Therefore there is a need for a method that will automate the counting and area measuring of particles within the range of from one micron to one millimeter across.